As described, for example, in WO 2014/076558 A2, Jacquard machines are used to bring the warp threads in a weaving machine into the correct position per weaving cycle in order to realize, in combination with the weft threads, a desired weave structure having a desired pattern. The warp threads are brought into the desired position with the aid of pulley mechanisms. In a pulley mechanism of this type, a pulley is provided with an upper and a lower pulley wheel. Examples of such pulleys are known, for example, from CH 380 046 A, CN 203 229 633 U, EP 0 526 820 A1 and CH 367 452 A.
Pulley mechanisms of this type are used, for example, in Jacquard machines for moving the warp threads of single-piece, flat looms. In this case, an upper pulley cord is passed around the upper pulley wheel in, this cord is provided with two corresponding hooks (complementary set of hooks), which can selectively move in tandem, for example in counterphase, with two corresponding knives, wherein the motion of the corresponding hooks is translated via the upper pulley cord into a rotation of the upper pulley wheel. By influencing of the hooks with the aid of one or more associated selectors, for example electromagnetic selectors, the hooks are secured in their uppermost or in their lowermost position (depending on the design) for the duration of one or more weaving cycles. Around the lower pulley wheel a lower pulley cord is passed, which is connected at one end to one or more heddles, which are provided with an opening (heddle eye), through which a warp thread runs, for adjustment of the position of this warp thread. Such a heddle is spring-loaded, whilst the other end of the lower pulley cord is held at a well-defined position in the Jacquard machine.
A similar pulley mechanism is used in multi-rapier weaving machines, which are provided to be able to introduce more than one weft per weaving cycle at different weft insertion levels. The associated pulley mechanism can then comprise a plurality of pulleys and/or extra reversing wheels.
In view of the increasing trend to weave fabrics of higher densities and/or to provide more colours in a fabric, higher and higher requirements are being imposed on Jacquard machines regarding the number of pulley mechanisms which, for a same volume, can be accommodated in a Jacquard machine. All solutions for making a Jacquard machine more compact are consequently of particularly great importance. In order to be able to achieve this, the pulleys are preferably designed as light and as cheap as possible, whilst they have to be able to take up as much load as possible per unit of volume.
Various pulleys have already been developed with this object in mind.
In a first known compact pulley, the pulley wheels are formed by moulding a plastics wheel disc around a central upright flange of a metal shaft. This upright flange, which is provided on the centre of the metal shaft, forms in this way the core of the pulley wheel. Two flank bodies, which form a housing for this pulley, are provided with recesses in which the ends of the shaft are rotatably fitted, so that the shaft, with the pulley wheel fastened centrally hereto, is arranged rotatably with respect to these flank bodies. For this purpose, the flank bodies must however be designed sufficiently rigid.
In a second, yet more compact known pulley the metal shafts are hence clamped in recesses of the flank bodies, wherein plastics pulley wheels are fitted rotatably around these shafts. By virtue of the clamping, the flank bodies are in this way also axially secured by the shafts. At the ends of these shafts, the flank bodies cannot be displaced outwardly or inwardly in the pulley, since the clamping with the shafts prevents this. As a result of this axial securement, these flank bodies can themselves be designed less rigid, and thus more compact and/or lighter and/or cheaper, or this pulley can have a longer working life for a same compactness.